Add checking changePassword None in _action_change_password(v2)

Current v2 api can not pass test_change_password_adminpass_none,
if passing body = {'changePassword': None} to _action_change_password
it will case argument of type 'NoneType' is not iterable.

Partially implements blueprint v2-on-v3-api
Change-Id: Ic88e6f600f09282cfb73bd6ccb7a89d34a7b0e59

nova/api/openstack/compute/servers.py

@@ -880,7 +880,7 @@ def _flavor_id_from_req_data(self, data):
     @wsgi.action('changePassword')
     def _action_change_password(self, req, id, body):
         context = req.environ['nova.context']
-        if ('changePassword' not in body
+        if (not body.get('changePassword')
                 or 'adminPass' not in body['changePassword']):
             msg = _("No adminPass was specified")
             raise exc.HTTPBadRequest(explanation=msg)

nova/tests/unit/api/openstack/compute/contrib/test_admin_password.py

@@ -144,7 +144,3 @@ def is_loaded(self, ext):
 
     def _check_status(self, expected_status, res, controller_method):
         self.assertEqual(expected_status, res.status_int)
-
-    def test_change_password_adminpass_none(self):
-        # TODO(eliqiao): need to handle adminpass is None in v2 api
-        pass